The fund was to release preliminary data Wednesday showing that 87 officers died in the line of duty between Jan. 1 and June 30. That's up sharply from 61 officers killed during the first six months of last year.
The 2010 deaths were spread across 36 states and Puerto Rico, with California, Texas and Florida showing the most fatalities. Other states on the list included Maryland, where a state trooper was fatally shot June 11, and Virginia. Five officers working for federal agencies also died in various states.
Firearm and traffic deaths jumped in the last six months, compared with the same period in 2009.
Last year, overall officer fatalities had reached their lowest level in five decades.
"We were hoping to see those numbers continue to go down," said Kevin P. Morison, a fund spokesman. "It points to the dangers officers continue to face."
Almost half the deaths came from car and motorcycle crashes and officers being hit outside their vehicles. Five officers who were struck on the road died during a three-week period last month in California, Massachusetts and New Jersey.
Of the 31 officers killed by gunfire, six died in "cluster killings" -- three separate shootings that targeted multiple officers.
Eugene O'Donnell, professor of police studies at John Jay College of Criminal Justice in New York, said the number of officer fatalities fluctuates from year to year. However, he said he has noticed an "alarming frequency" of people targeting police.
"There has been a spate of particularly brutal and senseless attacks on the police," said O'Donnell, a former police officer and prosecutor in New York. "It seems to me, an unprecedented level of disrespect and willingness to challenge police officers all over the place."
He said a rise in mental health problems and scathing criticism of police, such as the comments found on some blogs, could be fueling the brazenness and disregard for authority.
John Firman, director of research at the Alexandria, Va.-based International Association of Chiefs of Police, said his group is working to reduce rampant gun violence to which officers find themselves responding.
In addition, the association is working with the memorial fund, the FBI and other groups to create a Center for the Prevention of Violence Against Police to study the issue in depth. "We think this is awfully urgent," Firman said.
The memorial fund released the report with Concerns of Police Survivors Inc., a group that helps families of fallen officers. The fund adds the names of officers killed in the line of duty to its monument in Washington.